Construction of Polymer Recycling System Based on Equilibrium Polymerization

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This work dealt with (1) cationic equilibrium polymerization of spiro orthoesters (SOEs) and bicyclo orthoester (BOEs), (2) depolymerization of the obtain polymers, (3) reversible cationic crosslinking and decrosslinking between bifunctional SOEs and BOEs and the network polymers, (4) reversible cationic crosslinking and decrosslinking between SOE and BOE-based linear polymers and network polymers. SOEs gave poly(cyclic orthoester)s by single ring-opening polymerization in the presence of acid catalysts, and this process underwent equilibrium polymerization. We applied the function of equilibrium polymerization to chemical recycling of polymeric materials. Dithiollinked bifunctional spiro orthoester monomers afforded the corresponding crosslinked polymers at 0℃ in the presence of CFィイD23ィエD2COィイD22ィエD2H in bulk, and the resulted crosslinked polymers were efficiently converted into the original bifunctional spiro orthoesters by decrosslinking at room temperature in the presence of CFィイD23ィエD2COィイD22ィエD2H in CHィイD22ィエD2ClィイD22ィエD2. Further, acid-catalyzed reversible crosslinking-decrosslinking of a polymer having a spiro orthoester group in the side chain was carried out. The copolymer obtained by the radical copolymerization of 2-methylene-1,4,6-trioxaspiro[4.6]undecane with acrylonitrile was treated with CFィイD23ィエD2COィイD22ィエD2H at -10℃ in CHィイD22ィエD2ClィイD22ィエD2 to afford the crosslinked polymer quantitatively.The crosslinked polymer was then treated with CFィイD23ィエD2COィイD22ィエD2H at room temperature at a low concentration in CHィイD22ィエD2ClィイD22ィエD2 to recover the original polymer.